The present invention relates to an image display method, image display apparatus and image-based diagnostic apparatus. More particularly, the invention relates to an image display method, image display apparatus and image-based diagnostic apparatus capable of making the image display swiftly responsive to the operator's action of altering the window level and/or window width.
FIG. 7 is a block diagram showing the principal portion of a conventional image-based diagnostic apparatus. The image-based diagnostic apparatus 500 consists of an X-ray TV 20 which produces an X-ray transparency image of a subject body and evaluates pixels of the image, and an image display apparatus 50 which displays an image based on the values of pixels.
The image display apparatus 50 includes an operation panel 51 used by the operator, with window level alteration keys 1a for altering the window level WL and window width alteration keys 1b for altering the window width WW being laid out, a window setting circuit 52 which initializes a lookup table (LUT) 3 based on the default window level WL0 and default window width WW0 and also revises the entire contents of LUT 3 in accordance with an immediate window level WL and window width WW inresponse to the operation of a window level alteration key la and/or window width alteration key 1b, the LUT 3 which converts pixel values of an X-ray transparency image into values for display, and a display device 4 such as a CRT display device.
FIG. 8A shows window C1 having window level WL1 and window width WW1, and FIG. 8B shows the contents of LUT 3 for the window C1.
This LUT 3 converts pixel values ranging from "-32768" to "32768" into display values ranging from "0 (black)" to "255 (white)".
In FIG. 8A, the window level WL1 indicates the center pixel value of the range of pixel values to be converted into display values of "1" to "254" between the minimum display value "0" and the maximum display value "255". The window width WW1 indicates the width of the conversion range.
In FIG. 9A, when the operator operates a window level alteration key 1a and window width alteration key 1b to alter the window level from WL1 to WL2 and alter the window width from WW1 to WW2, the window setting circuit 52 revises the entire contents of LUT 3 in accordance with the new window level WL2 and window width WW2. FIG. 9B show the contents of LUT 3 for window C2.
The foregoing conventional technique is disclosed in Japanese Patent Laid-open Publication No. Hei-8-7074, for example.
As described above, the conventional image display apparatus 50 or image-based diagnostic apparatus 500 is designed to revise the entire contents of LUT 3 in response to the operator's action of altering the window level and/or window width.
However, it takes a long time for the LUT 3 to revise 65536 pieces of data, and therefore the image display cannot respond swiftly to the alteration of the window level and/or window width.